U.S. patent number 11,426,135 [Application Number 17/250,543] was granted by the patent office on 2022-08-30 for multi-modal compton and single photon emission computed tomography medical imaging system.
This patent grant is currently assigned to Siemens Medical Solutions USA, Inc.. The grantee listed for this patent is Siemens Medical Solutions USA, Inc.. Invention is credited to Miesher Rodrigues, Alexander Hans Vija.
United States Patent |
11,426,135 |
Vija , et al. |
August 30, 2022 |
Multi-modal Compton and single photon emission computed tomography
medical imaging system
Abstract
A multi-modality imaging system allows for selectable
photoelectric effect and/or Compton effect detection. The camera or
detector is a module with a catcher detector. Depending on the use
or design, a scatter detector and/or a coded physical aperture are
positioned in front of the catcher detector relative to the patient
space. For low energies, emissions passing through the scatter
detector continue through the coded aperture to be detected by the
catcher detector using the photoelectric effect. Alternatively, the
scatter detector is not provided. For higher energies, some
emissions scatter at the scatter detector, and resulting emissions
from the scattering pass by or through the coded aperture to be
detected at the catcher detector for detection using the Compton
effect. Alternatively, the coded aperture is not provided. The same
module may be used to detect using both the photoelectric and
Compton effects where both the scatter detector and coded aperture
are provided with the catcher detector. Multiple modules may be
positioned together to form a larger camera, or a module is used
alone. By using modules, any number of modules may be used to fit
with a multi-modality imaging system. One or more such modules may
be added to another imaging system (e.g., CT or MR) for a
multi-modality imaging system.
Inventors: |
Vija; Alexander Hans (Evanston,
IL), Rodrigues; Miesher (Buffalo Grove, IL) |
Applicant: |
Name |
City |
State |
Country |
Type |
Siemens Medical Solutions USA, Inc. |
Malvern |
PA |
US |
|
|
Assignee: |
Siemens Medical Solutions USA,
Inc. (Malvern, PA)
|
Family
ID: |
1000006530234 |
Appl.
No.: |
17/250,543 |
Filed: |
August 7, 2018 |
PCT
Filed: |
August 07, 2018 |
PCT No.: |
PCT/US2018/045466 |
371(c)(1),(2),(4) Date: |
February 02, 2021 |
PCT
Pub. No.: |
WO2020/032922 |
PCT
Pub. Date: |
February 13, 2020 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20210282728 A1 |
Sep 16, 2021 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B
6/037 (20130101); G01N 23/20066 (20130101); A61B
6/4266 (20130101); A61B 6/4411 (20130101); A61B
6/4275 (20130101); A61B 6/4417 (20130101); G01R
33/481 (20130101); G01N 2223/50 (20130101); G01N
2223/063 (20130101) |
Current International
Class: |
A61B
6/00 (20060101); A61B 6/03 (20060101); G01N
23/20066 (20180101); G01R 33/48 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2060932 |
|
Mar 2017 |
|
EP |
|
2004125757 |
|
Apr 2004 |
|
JP |
|
2005514975 |
|
May 2005 |
|
JP |
|
2008522168 |
|
Jun 2008 |
|
JP |
|
2017522543 |
|
Aug 2017 |
|
JP |
|
2012058731 |
|
May 2012 |
|
WO |
|
Other References
Ordonez, Caesar E., Alexander Bolozdynya, and Wei Chang. "Doppler
broadening of energy spectra in Compton cameras." Nuclear Science
Symposium, 1997. IEEE. vol. 2. IEEE, 1997. cited by applicant .
International Search Report for Corresponding International
Application No. PCT/US2018/045466, dated Jun. 17, 2019. cited by
applicant.
|
Primary Examiner: Song; Hoon K
Claims
We claim:
1. A multi-modality medical imaging system comprising: a first
module having a first catcher detector, a position for a first
scatter detector spaced from the catcher detector, and a position
for a first physical aperture between a patient space and the first
catcher detector; and an image processor configured to determine
angles of incidence for Compton events where the first scatter
detector is included in the first module and to count photoelectric
events where the first physical aperture is included in the first
module.
2. The multi-modality medical imaging system of claim 1 wherein the
first physical aperture is at the position of the first physical
aperture and the first physical aperture comprises a coded aperture
of lead or tungsten.
3. The multi-modality medical imaging system of claim 2 wherein the
coded aperture comprises a time-encoded aperture rotatable about an
axis and/or translatable in a plane perpendicular to the axis to
cast shadows with different positions on the first catcher
detector.
4. The multi-modality medical imaging system of claim 1 wherein the
first physical aperture is at the position of the first physical
aperture and the first catcher detector and the first physical
aperture are parallel, the first physical aperture having a shadow
on the first catcher detector in a center region of the first
catcher detector and not an outer region of the first catcher
detector, and wherein the image processor is configured to count
the photoelectric events from the center region and not the outer
region and to determine the angles of incidence for the Compton
events with photon interaction events primarily from the outer
region.
5. The multi-modality medical imaging system of claim 1 further
comprising a second module having a second catcher detector with
positions for a second scatter detector and a second physical
aperture; and wherein the first and second modules are three, five,
or six sided in cross-section orthogonal to a radial from a patient
space.
6. The multi-modality medical imaging system of claim 5 wherein the
first and second modules are cylindrically symmetric, a narrowest
end of each of the first and second modules being closest to a
patient space of the medical imaging system, a widest end of each
of the first and second modules being furthest from the patient
space.
7. The multi-modality medical imaging system of claim 1 wherein the
first module further comprises circuit boards orthogonal to the
first catcher detector, application specific integrated circuits
with the first catcher detector, flexible circuits connecting the
application specific integrated circuits to the circuit boards, and
positions for one or more additional catcher and/or scatter layers
between the first catcher layer and the first scatter layer.
8. The multi-modality medical imaging system of claim 1 wherein the
first module is part of a ring or partial ring around a patient
space of the medical imaging system.
9. The multi-modality medical imaging system of claim 8 further
comprising additional modules for the ring or partial ring and for
another ring or partial ring intersecting with the ring or partial
ring at two of the additional modules.
10. The multi-modality medical imaging system of claim 9 wherein
the ring or partial ring and the other ring or partial ring are 90
degrees apart.
11. The multi-modality medical imaging system of claim 8 further
comprising an additional ring or partial ring of modules axially
adjacent to the ring or partial ring with the first module, the
additional ring or partial ring and the ring or partial ring
forming part of a geodesic dome.
12. The multi-modality medical imaging system of claim 1 wherein
the first scatter detector is at the position of the first scatter
detector in the module, the first physical aperture is at the
position of the first physical aperture in the module, and wherein
the image processor is configured to generate a single photon
emission computed tomography image from the count and a Compton
image from the Compton events, and further comprising a display
configured to display the single photon emission computed
tomography image and the Compton image.
13. The multi-modality medical imaging system of claim 1 wherein
the first scatter detector is included in the first module at the
position for the first scatter detector where relatively higher
energies are to be detected and wherein the first physical aperture
is included in the first module at the position for the first
physical aperture where relatively lower energies are to be
detected.
14. A medical imaging system comprising: solid-state detector
modules each with a first detector arranged to be used with either
or both of a plate forming a coded aperture and a scatter detector;
the solid-state detector modules having three, five, or six sides
in a cross-section normal to a radial from longitudinal patient
axis such that the solid-state detector modules stack together to
form part of a geodesic dome.
15. The medical imaging system of claim 14 wherein each of the
solid-state detector modules further comprises the scatter detector
and the plate, the plate being between the scatter detector and the
first detector, further comprising an image processor configured to
detect emissions with a photoelectric effect using the plate and
the first detector and to detect emissions with a Compton effect
using the scatter detector and the first detector.
16. The medical imaging system of claim 14 wherein each of the
solid-state detector modules includes the plate, the plate being
rotatable and/or translatable relative to the first detector within
the respective solid-state detector modules.
17. The medical imaging system of claim 14 wherein the stack to
form the part of the geodesic dome comprises two separate rings
sharing two of the solid-state modules.
18. A method for forming a Compton camera and/or a single photon
emission computed tomography camera, the method comprising: housing
a catcher detector in a housing, the catcher detector arranged to
be usable for relatively lower emission energies with a coded
aperture and to be usable for relatively higher emission energies
with a scatter detector, the housing shaped as a part of a geodesic
dome; and mounting the housing relative to a patient bed with a
selected one or both of the coded aperture and the scatter
detector.
19. The method of claim 18 wherein mounting comprises forming a
ring or partial ring with the housing and additional ones of the
housing as part of a multi-modality system including the Compton
camera using the scatter detector in the housing and a single
photon emission computed tomography imaging system using the coded
aperture in the housing.
20. The method of claim 18 further comprising: detecting a first
emission as a Compton event with the scatter detector and the
catcher detector; and detecting a second emission as a
photoelectric event passing through the coded aperture with the
catcher detector.
Description
BACKGROUND
The present embodiments relate to nuclear imaging, such as single
photon emission computed tomography (SPECT) imaging. Slowly
rotating large field-of-view SPECT systems rely on the existence of
a physical collimator. A parallel-hole collimator, which combined
with a position-sensitive detector, forms the image. Relying on a
photoelectric effect for detecting emissions from a radioisotope in
the patient, these collimated SPECT systems are limited to
low-energy photon emitting isotopes, such as Tc99m. Image quality
and efficiency are key parameters of any image formation system for
SPECT medical applications. Increased sensitivity and image quality
are desirable features in new SPECT image formation systems as well
as the added possibility of imaging higher photon energies.
The Compton effect allows for imaging higher energies. Compton
imaging systems are constructed as test platforms, such as
assembling a scatter ring and then a catcher ring mounted to a
large framework. Electronics are connected to detect Compton-based
events from emissions of a phantom. Compton imaging systems have
failed to address design and constraint requirements for practical
use in any commercial clinical settings. Current proposals lack the
ability to be integrated into imaging platforms in the clinic or
lack the design and constraint requirements (i.e., flexibility and
scalability) to address commercial needs.
SUMMARY
By way of introduction, the preferred embodiments described below
include methods and systems for medical imaging. A multi-modality
imaging system allows for selectable photoelectric effect and/or
Compton effect detection. The camera or detector is a module with a
catcher detector. Depending on the use or design, a scatter
detector and/or a coded physical aperture are positioned in front
of the catcher detector relative to the patient space. For low
energies, emissions passing through the scatter detector continue
through the coded aperture to be detected by the catcher detector
using the photoelectric effect. Alternatively, the scatter detector
is not provided. For higher energies, some emissions scatter at the
scatter detector, and resulting emissions from the scattering pass
by or through the coded aperture to be detected at the catcher
detector for detection using the Compton effect. Alternatively, the
coded aperture is not provided. The same module may be used to
detect using both the photoelectric and Compton effects where both
the scatter detector and coded aperture are provided with the
catcher detector. Multiple modules may be positioned together to
form a larger camera or a module is used alone. By using modules,
any number of modules may be used to fit with a multi-modality
imaging system. One or more such modules may be added to another
imaging system (e.g., CT or MR) for a multi-modality imaging
system.
In a first aspect, multi-modality medical imaging system includes a
first module having a first catcher detector, a position for a
first scatter detector spaced from the catcher detector, and a
position for a first physical aperture between a patient space and
the first catcher detector. An image processor is configured to
determine angles of incidence for Compton events where the first
scatter detector is included in the first module and to count
photoelectric events where the first physical aperture is included
in the first module.
In a second aspect, a medical imaging system includes solid-state
detector modules each with a first detector arranged to be used
with either or both of a plate forming a coded aperture and a
scatter detector. The solid-state detector modules having three,
five, or six sides in a cross-section normal to a radial from
longitudinal patient axis such that the solid-state detector
modules stack together to form part of a geodesic dome.
In a third aspect, a method is provided for forming a Compton
camera and/or a single photon emission computed tomography camera.
A catcher detector is housed in a housing. The catcher detector
arranged to be usable for relatively lower emission energies with a
coded aperture and to be usable for relatively higher emission
energies with a scatter detector. The housing is shaped as a part
of a geodesic dome. The housing is mounted relative to a patient
bed with a selected one or both of the coded aperture and the
scatter detector.
The present invention is defined by the following claims, and
nothing in this section should be taken as a limitation on those
claims. Further aspects and advantages of the invention are
discussed below in conjunction with the preferred embodiments and
may be later claimed independently or in combination.
BRIEF DESCRIPTION OF THE DRAWINGS
The components and the figures are not necessarily to scale,
emphasis instead being placed upon illustrating the principles of
the invention. Moreover, in the figures, like reference numerals
designate corresponding parts throughout the different views.
FIG. 1 is perspective view of multiple modules of a Compton camera
according to one embodiment;
FIG. 2 illustrates an example scatter detector;
FIG. 3 illustrates an example catcher detector;
FIG. 4A is a side view of one embodiment of a Compton camera, FIG.
4B is an end view of the Compton camera of FIG. 4A, and FIG. 4C is
a detail view of a part of the Compton camera of FIG. 4B;
FIG. 5 is a perspective view of one embodiment of a Compton camera
in a medical imaging system;
FIG. 6 is a perspective view of one embodiment of a full-ring
Compton camera in a medical imaging system;
FIG. 7 is a perspective view of one embodiment of a partial-ring
Compton camera in a medical imaging system;
FIG. 8 is a perspective view of one embodiment of a full-ring
Compton camera with partial-rings in axial extension in a medical
imaging system;
FIG. 9 is a perspective view of one embodiment of a single
module-based Compton camera in a medical imaging system;
FIG. 10 is a flow chart diagram of an example embodiment of a
method for forming a Compton camera;
FIG. 11 illustrates the scatter and catcher detectors with an
intervening coded aperture for imaging using both photoelectric and
Compton effects;
FIG. 12 is a perspective view of one embodiment of a full-ring
multi-modality camera from modules shaped for a geodesic dome-like
structure;
FIG. 13 is a perspective view of one embodiment of a dual-ring
multi-modality camera from modules shaped for a geodesic dome-like
structure;
FIG. 14 is a perspective view of one embodiment of multiple
full-rings stacked axially in a multi-modality camera from modules
shaped for a geodesic dome-like structure;
FIG. 15 is a perspective view of one embodiment of a multi-modality
camera formed from three modules shaped for a geodesic dome-like
structure; and
FIG. 16 is a perspective view of one embodiment of a photoelectric
effect camera formed from three modules shaped for a geodesic
dome-like structure.
DETAILED DESCRIPTION OF THE DRAWINGS AND PRESENTLY PREFERRED
EMBODIMENTS
FIGS. 1-9 are directed to a multi-modality compatible Compton
camera. A modular design is used to form the Compton camera for use
with various other imaging modalities. FIGS. 11-16 are directed to
a modular design with a catcher detector that may be used with
either a scatter detector for Compton imaging or a coded aperture
for SPECT imaging. The module provides positions for either or both
of the scatter detector and coded aperture. After a summary of the
selectable SPECT-Compton embodiments, the Compton camera of FIGS.
1-9 is described. Many of the features and components of the
Compton camera of FIGS. 1-9 are used in the SPECT-Compton
embodiments described in FIGS. 11-16.
For the selectable SPECT-Compton embodiments, a clinical
multi-modality compatible and modular camera is provided for
medical imaging. For lower energy emissions, a coded aperture may
be included in each module for SPECT operation. For higher energy
emissions, a scatter detector may be included in each module for
Compton operation. The modular design allows enough flexibility
that the selectable SPECT-Compton camera may be added to existing
computed tomography (CT), magnetic resonance (MR), or positron
emission tomography (PET) platforms, either as axially separated
systems, or as fully integrated systems. Modularity allows
efficient manufacturing and serviceability. Increased sensitivity
and image quality are desirable features in new SPECT image
formation systems as well as the added possibility of imaging
higher photon energies. Hybrid imaging uses the Compton effect for
higher energies and the photoelectric effect with physical
collimation for low energies .about.140.5 keV where both the
scatter detector and coded aperture are provided in the respective
positions of a same module.
Referring to FIGS. 1-9, a medical imaging system includes a
multi-modality compatible Compton camera with segmented detection
modules. The Compton camera, such as a Compton camera ring, is
segmented into modules that house the detection units. Each module
is independent, and when assembled into a ring or partial ring, the
modules may communicate with each other. The modules are
independent yet can be assembled into a multi-module unit that
produces Compton scattering-based images. Cylindrically symmetric
modules or spherical shell segmented modules may be used.
The scatter-catcher pair, modular arrangement allows efficient
manufacturing, is serviceable in the field, and is cost and energy
efficient. The modules allow for the design freedom to change the
radius for each radial detection unit, angular span of one module,
and/or axial span. The scatter-catcher pair modules are
multi-modality compatible and/or form a modular ring Compton camera
for clinical emission imaging. This design allows flexibility, so
the Compton camera may be added to existing computed tomography
(CT), magnetic resonance (MR), positron emission tomography (PET)
or other medical imaging platforms, either as axially separated
systems or as fully integrated systems. Each module may address
heat dissipation, data collection, calibration, and/or allow for
efficient assembly as well as servicing.
Each scatter-catcher paired module is formed from commercially
suitable solid-state detector modules (e.g., Si, CZT, CdTe, HPGe or
similar), allowing for an energy range of 100-3000 keV. Compton
imaging may be provided with a wider range of isotope energies
(>2 MeV), enabling new tracers/markers through selection of the
scatter-catcher detectors. The modularity allows for individual
module removal or replacement, allowing for time and cost-efficient
service. The modules may be operated independently and isolated or
may be linked for cross-talk, allowing for improved image quality
and higher efficiency in detecting Compton events using a scatter
detector of one module and a catcher detector of another
module.
The modularity allows for flexible design geometry optimized to
individual requirements, such as using a partial ring for
integration with a CT system (e.g., connected between the x-ray
source and detector), a few modules (e.g., tiling) used for
integration with a single photon emission computed tomography gamma
camera or other space limited imaging system, or a full ring.
Functional imaging based on Compton-detected events may be added to
other imaging systems (e.g., CT, MR, or PET). Multiple full or
partial rings may be placed adjacent to each other for greater
axial coverage of the Compton camera. A dedicated or stand-alone
Compton-based imaging system may be formed. In one embodiment, the
modules include a collimator for lower energies (e.g., <300
keV), providing for multichannel and multiplexed imaging (e.g.,
high energies using the scatter-catcher detectors for Compton
events and low energies using one of the detectors for SPECT or PET
imaging). The modules may be stationary or fast rotating (0.1
rpm<<.omega.<<240 rpm). The dimensional, installation,
service, and/or cost constraints are addressed by the
scatter-catcher paired modules.
FIG. 1 shows one embodiment of modules 11 for a Compton camera.
Four modules 11 are shown, but additional or fewer modules may be
used. The Compton camera is formed from one or more modules,
depending on the desired design of the Compton camera.
The Compton camera is for medical imaging. A space for a patient
relative to the modules is provided so that the modules are
positioned to detect photons emitted from the patient. A
radiopharmaceutical in the patient includes a radio-isotope. A
photon is emitted from the patient due to decay from the
radio-isotope. The energy from the radio-isotope may be 100-3000
keV, depending on the material and structure of the detectors. Any
of various radio-isotopes may be used for imaging a patient.
Each of the modules 11 includes the same or many of the same
components. A scatter detector 12, a catcher detector 13, circuit
boards 14, and baffle 15 are provided in a same housing 21.
Additional, different, or fewer components may be provided. For
example, the scatter detector 12 and catcher detector 13 are
provided in the housing 21 without other components. As another
example, a fiber optic data line 16 is provided in all or a sub-set
of the modules 11.
The modules 11 are shaped for being stacked together. The modules
11 mate with each other, such as having matching indentation and
extensions, latches, tongue-and-grooves, or clips. In other
embodiments, flat or other surfaces are provided for resting
against each other or a divider. Latches, clips, bolts,
tongue-and-groove or other attachment mechanisms for attaching a
module 11 to any adjacent modules 11 are provided. In other
embodiments, the module 11 attaches to a gantry or other framework
with or without direct connection to any adjacent modules 11.
The connection or connections to the other modules 11 or gantry may
be releasable. The module 11 is connected and may be disconnected.
The connection may be releasable, allowing removal of one module 11
or a group of modules 11 without removing all modules 11.
For forming a Compton camera from more than one module 11, the
housing 21 and/or outer shape of the modules 11 is wedge shaped.
The modules 11 may be stacked around an axis to form a ring or
partial ring due to the wedge shape. The part closer to the axis
has a width size that is narrower along a dimension perpendicular
to the axis than a width size of a part further from the axis. In
the modules 11 of FIG. 1, the housings 21 have the widest part
furthest from the axis. In other embodiments, the widest part is
closer to the axis but spaced away from the narrowest part closest
to the axis. In the wedge shape, the scatter detector 12 is nearer
to the narrower part of the wedge shape than the catcher detector
13. This wedge shape in cross-section along a plane normal to the
axis allows stacking of the modules 11 in abutting positions,
adjacently, and/or connected to form at least part of a ring about
the axis.
The taper of the wedge provides for a number N of modules 11 to
form a complete ring around the axis. Any number N may be used,
such as N=10-30 modules. The number N may be configurable, such as
using different housings 21 for different numbers N. The number of
modules 11 used for a given Compton camera may vary, depending on
the design of the Compton camera (e.g., partial ring). The wedge
shape may be provided along other dimensions, such as having a
wedge shape in a cross-section parallel to the axis.
The modules 11 as stacked are cylindrically symmetric as connected
with a gantry of a medical imaging system. A narrowest end of the
wedged cross-section is closest to a patient space of the medical
imaging system and a widest end of the wedged cross-section may be
furthest from the patient space. In alternative embodiments, other
shapes than wedge allowing for stacking together to provide a ring
or generally curved shape of the stack may be provided.
The housing 21 is metal, plastic, fiberglass, carbon (e.g., carbon
fiber), and/or other material. In one embodiment, different parts
of the housing 21 are of different materials. For example, tin is
used for the housing around the circuit boards 14. Aluminum is used
to hold the scatter detector 12 and/or catcher detector 13. In
another example, the housing 12 is of the same material, such as
aluminum.
The housing 21 may be formed from different structures, such as end
plates having the wedge shape, sheets of ground plane housing the
circuit boards 14, and separate structure for walls holding the
scatter detector 12 and catcher detector 13 where the separate
structure is formed of material through which photons of a desired
energy from a Compton event may pass (e.g., aluminum or carbon
fiber). In alternative embodiments, walls are not provided for the
modules 11 between the end plates for a region where the scatter
detector 12 and/or catcher detector 13 are positioned, avoiding
interference of photons passing from the scatter detector 12 of one
module 11 to a catcher detector 13 of another module 11. The
housing 21 by and/or for holding the detectors 12, 13 is made of
low attenuating material, such as aluminum or carbon fiber.
The housing 21 may seal the module or includes openings. For
example, openings for air flow are provided, such as at a top of
widest portion of the wedge shape at the circuit boards 14. The
housing 21 may include holes, grooves, tongues, latches, clips,
stand-offs, bumpers, or other structures for mounting, mating,
and/or stacking.
Each of the solid-state detector modules 11 includes both scatter
and catcher detectors 12, 13 of a Compton sensor. By stacking each
module, the size of the Compton sensor is increased. A given module
11 itself may be a Compton sensor since both the scatter detector
12 and catcher detector 13 are included in the module.
The modules 11 may be separately removed and/or added to the
Compton sensor. For a given module 11, the scatter detector 12
and/or catcher detector 13 may be removable from the module 11. For
example, a module 11 is removed for service. A faulty one or both
detectors 12, 13 are removed from the module 11 for replacement.
Once replaced, the refurbished module 11 is placed back in the
medical imaging system. Bolts, clips, latches, tongue-and-groove,
or other releasable connectors may connect the detectors 12, 13 or
part of the housing 21 for the detectors 12, 13 to the rest of the
module 11.
The scatter detector 12 is a solid-state detector. Any material may
be used, such as Si, CZT, CdTe, HPGe, and/or other material. The
scatter detector 12 is created with wafer fabrication at any
thickness, such as about 4 mm for CZT. Any size may be used, such
as about 5.times.5 cm. FIG. 2 shows a square shape for the scatter
detector 12. Other shapes than square may be used, such as
rectangular. For the modules 11 of FIG. 1, the scatter detector 12
may be rectangular extending between two wedge-shaped
end-plates.
In the module 11, the scatter detector 12 has any extent. For
example, the scatter detector 12 extends from one wedge-shaped end
wall to the other wedge-shaped end wall. Lesser or greater extent
may be provided, such as extending between mountings within the
module 11 or extending axially beyond one or both end-walls. In one
embodiment, the scatter detector 12 is at, on, or by one end wall
without extended to another end wall.
The scatter detector 12 forms an array of sensors. For example, the
5.times.5 cm scatter detector 12 of FIG. 2 is a 21.times.21 pixel
array with a pixel pitch of about 2.2 mm. Other numbers of pixels,
pixel pitch, and/or size of arrays may be used.
The scatter detector 12 includes semiconductor formatted for
processing. For example, the scatter detector 12 includes an
application specific integrated circuit (ASIC) for sensing photon
interaction with an electron in the scatter detector 12. The ASIC
is collocated with the pixels of the scatter detector 12. The ASIC
is of any thickness. A plurality of ASICs may be provided, such as
9 ASICS in a 3.times.3 grid of the scatter detector 12.
The scatter detector 12 may operate at any count rate, such as
>100 kcps/mm. Electricity is generated by a pixel due to the
interaction. This electricity is sensed by the application specific
integrated circuit. The location, time, and/or energy is sensed.
The sensed signal may be conditioned, such as amplified, and sent
to one or more of the circuit boards 14. A flexible circuit, wires,
or other communications path carries the signals from the ASIC to
the circuit board 14.
Compton sensing operates without collimation. Instead, a fixed
relationship between energy, position, and angle of a photon
interaction at the scatter detector 12 relative to a photon
interaction at the catcher detector 13 is used to determine the
angle of the photon entering the scatter detector 12. A Compton
process is applied using the scatter detector 12 and the catcher
detector 13.
The catcher detector 13 is a solid-state detector. Any material may
be used, such as Si, CZT, CdTe, HPGe, and/or other material. The
catcher detector 13 is created with wafer fabrication at any
thickness, such as about 10 mm for CZT. Any size may be used, such
as about 5.times.5 cm. The size may be larger along at least one
dimension than the scatter detector 12 due to the wedge shape and
spaced apart positions of the scatter detector 12 and the catcher
detector 13. FIG. 3 shows a rectangular shape for the catcher
detector 13 but other shapes may be used. For the modules 11 of
FIG. 1, the catcher detector 13 may be rectangular extending
between two end-plates where the length is the same as and the
width is greater than the scatter detector 12.
The catcher detector 12 forms an array of sensors. For example, the
5.times.6 cm catcher detector 13 of FIG. 3 is a 14.times.18 pixel
array with a pixel pitch of about 3.4 mm. The pixel size is larger
than the pixel size of the scatter detector 12. The number of
pixels is less than the number of pixels of the scatter detector
12. Other numbers of pixels, pixel pitch, and/or size of arrays may
be used. Other relative pixels sizes and/or numbers of pixels may
be used.
In the module 11, the catcher detector 13 has any extent. For
example, the catcher detector 13 extends from one wedge-shaped end
wall to the other wedge-shaped end wall. Lesser or greater extent
may be provided, such as extending between mountings within the
module 11 or extending axially beyond one or both end-walls. In one
embodiment, the catcher detector 13 is at, on, or by one end wall
without extending to another end wall.
The catcher detector 13 includes semiconductor formatted for
processing. For example, the catcher detector 13 includes an ASIC
for sensing photon interaction with an electron in the catcher
detector 13. The ASIC is collocated with the pixels of the catcher
detector 13. The ASIC is of any thickness. A plurality of ASICS may
be provided, such as 6 ASICS in a 2.times.3 grid of the catcher
detector 13.
The catcher detector 13 may operate at any count rate, such as
>100 kcps/mm. Electricity is generated by a pixel due to the
interaction. This electricity is sensed by the ASIC. The location,
time, and/or energy is sensed. The sensed signal may be
conditioned, such as amplified, and sent to one or more of the
circuit boards 14. A flexible circuit, wires, or other
communications path carries the signals from the ASIC to the
circuit board 14.
The catcher detector 13 is spaced from the scatter detector 12 by
any distance along a radial line from the axis or normal to the
parallel scatter and catcher detectors 12, 13. In one embodiment,
the separation is about 20 cm, but greater or lesser separation may
be provided. The space between the catcher detector 13 and the
scatter detector 12 is filled with air, other gas, and/or other
material with low attenuation for photons at the desired
energies.
The circuit boards 14 are printed circuit boards, but flexible
circuits or other materials may be used. Any number of circuit
boards 14 for each module may be used. For example, one circuit
board 14 is provided for the scatter detector 12 and another
circuit board 14 is provided for the catcher detector 13.
The circuit boards 14 are within the housing 21 but may extend
beyond the housing 21. The housing 21 may be grounded, acting as a
ground plane for the circuit boards 14. The circuit boards 14 are
mounted in parallel with each other or are non-parallel, such as
spreading apart in accordance with the wedge shape. The circuit
boards are positioned generally orthogonal to the catcher detector
13. Generally is used to account for any spread due to the wedge
shape. Brackets, bolts, screws, and/or stand-offs from each other
and/or the housing 21 are used to hold the circuit boards 14 in
place.
The circuit boards 14 connect to the ASICS of the scatter and
catcher detectors 12, 13 through flexible circuits or wires. The
ASICs output detected signals. The circuit boards 14 are
acquisition electronics, which process the detected signals to
provide parameters to the Compton processor 19. Any
parameterization of the detected signals may be used. In one
embodiment, the energy, arrival time, and position in
three-dimensions is output. Other acquisition processing may be
provided.
The circuit boards 14 output to each other, such as through a
galvanic connection within a module 11, to the data bridge 17,
and/or to a fiber optic data link 16. The fiber data link 16 is a
fiber optic interface for converting electrical signals to optical
signals. A fiber optic cable or cables provide the acquisition
parameters for events detected by the scatter and catcher detectors
12, 13 to the Compton processor 19.
The data bridge 17 is a circuit board, wires, flexible circuit,
and/or other material for galvanic connection to allow
communications between modules 11. A housing or protective plate
may cover the data bridge 17. The data bridge 17 releasably
connects to one or more modules 11. For example, plugs or mated
connectors of the data bridge 17 mate with corresponding plugs or
mated connectors on the housing 21 and/or circuit boards 14. A
latch, clip, tongue-and-groove, screw, and/or bolt connection may
be used to releasably hold the data bridge 17 in place with the
modules 11.
The data bridge 17 allows communications between the modules. For
example, the fiber data link 16 is provided in one modules 11 and
not another module 11. The cost of a fiber data link 16 in every
module 11 is avoided. Instead, the parameters output by the other
module 11 are provided via the data bridge 17 to the module 11 with
the fiber data link 16. The circuit board or boards 14 of the
module 11 with the fiber data link 16 route the parameter output to
the fiber data link 16, using the fiber data link 16 to report
detected events from more than one module 11. In alternative
embodiments, each module 11 includes a fiber data link 16, so the
data bridge 17 is not provided or communicates other
information.
The data bridge 17 may connect other signals between the modules
11. For example, the data bridge 17 includes a conductor for power.
Alternatively, a different bridge provides power to the modules 11
or the modules 11 are individually powered. As another example,
clock and/or synchronization signals are communicated between
modules 11 using the data bridge 17.
In the embodiment of FIG. 1, a separate clock and/or
synchronization bridge 18 is provided. The clock and/or
synchronization bridge 18 is a circuit board, wires, flexible
circuit, and/or other material for galvanic connection to allow
communication of clock and/or synchronization signals between
modules 11. A housing or protective plate may cover the clock
and/or synchronization bridge 18. The clock and/or synchronization
bridge 18 releasably connects to one or more modules 11. For
example, plugs or mated connectors of the clock and/or
synchronization bridge 18 mate with corresponding plugs or mated
connectors on the housing 21 and/or circuit boards 14. A latch,
clip, tongue-and-groove, screw, and/or bolt connection may be used
to releasably hold the clock and/or synchronization bridge 18 in
place with the modules 11.
The clock and/or synchronization bridge 18 may connect with the
same or different grouping of modules 11 as the data bridge 17. In
the embodiment shown in FIG. 1, the data bridge 17 connects between
pairs of modules 11 and the clock and/or synchronization bridge 18
connects over groups of four modules 11.
The clock and/or synchronization bridge 18 provides a common clock
signal and/or synchronization signals for synchronizing clocks of
the modules 11. One of the parameters formed by the circuit boards
14 of each module 11 is the time of detection of the event. Compton
detection relies on pairs of events--a scatter event and a catcher
event. Timing is used to pair events from the different detectors
12, 13. The common clocking and/or synchronization allows for
accurate pairing where the pair of events are detected in different
modules 11. In alternative embodiments, only scatter and catcher
events detected in a same module 11 are used, so the clock and/or
synchronization bridge 18 may not be provided.
Other links or bridges between different modules 11 may be
provided. Since the bridges 17, 18 are removable, individual
modules 11 may be removed for service while leaving remaining
modules 11 in the gantry.
Each module 11 is air cooled. Holes may be provided for forcing air
through the module 11 (i.e., entry and exit holes). One or more
baffles 15 may be provided to guide the air within the module 11.
Water, conductive transfer, and/or other cooling may be
alternatively or additionally provided.
In one embodiment, the top portion of the wedge-shape module 11 or
housing 21 is open (i.e., no cover on the side furthest from the
patient area). One or more baffles 15 are provided along the
centers of one or more circuit boards 14 and/or the housing 21. A
fan and heat exchanger 20 force cooled or ambient temperature air
into each module 11, such as along one half of the module 11 at a
location spaced away from the catcher detector 13 (e.g., top of the
module 11). The baffles 15 and/or circuit boards 14 guide at least
some of the air to the airspace between the scatter detector 12 and
the catcher detector 13. The air then passes by the baffles 15
and/or circuit boards 14 on another part (e.g., another half) of
the module 11 for exiting to the heat exchanger 20. Other routing
of the air may be provided.
The heat exchanger and fan 20 is provided for each individual
module 11, so may be entirely or partly within the module 11. In
other embodiments, ducting, baffles, or other structure route air
to multiple modules 11. For example, groups of four modules 11
share a common heat exchanger and fan 20, which is mounted to the
gantry or other framework for cooling the group of modules 11.
For forming a Compton sensor, one or more modules 11 are used. For
example, two or more modules 11 are positioned relative to a
patient bed or imaging space to detect photon emissions from the
patient. An arrangement of a greater number of modules 11 may allow
for detection of a greater number of emissions. By using the wedge
shape, modules 11 may be positioned against, adjacent, and/or
connected with each other to form an arc about the patient space.
The arc may have any extent. The modules 11 directly contact each
other or contact through spacers or the gantry with small
separation (e.g., 10 cm or less) between the modules 11.
In one example, four modules 11 are positioned together, sharing a
clock and/or synchronization bridge 18, one or more data bridges
17, and a heat exchanger and fan 20. One, two, or four fiber data
links 16 are provided for the group of modules 11. Multiple such
groups of modules 11 may be positioned apart or adjacent to each
other for a same patient space.
Due to the modular approach, any number of modules 11 may be used.
Manufacturing is more efficient and costly by building multiple of
the same component despite use of any given module 11 in a
different arrangement than used for others of the modules 11.
The fiber data links 16 of the modules 11 or groups of modules 11
connect to the Compton processor 19. The Compton processor 19
receives the values for the parameters for the different events.
Using the energy and timing parameters, scatter and catcher events
are paired. For each pair, the spatial locations and energies of
the pair of events are used to find the angle of incidence of the
photon on the scatter detector 12. The event pairs are limited to
events in the same module 11 in one embodiment. In another
embodiment, catcher events from the same or different modules 11
may be paired with scatter events from a given module 11. More than
one Compton processor 19 may be used, such as for pairing events
from different parts of a partial ring 40.
Once paired events are linked, the Compton processor 19 or another
processor may perform computed tomography to reconstruct a
distribution in two or three dimensions of the detected emissions.
The angle or line of incidence for each event is used in the
reconstruction.
FIGS. 4A-6 shows one example arrangement of modules 11. The modules
11 form a ring 40 surrounding a patient space. FIG. 4A shows four
such rings 40 stacked axially. FIG. 4B shows the scatter detectors
12 and corresponding catcher detectors 13 of the modules 11 in the
ring 40. FIG. 4C shows a detail of a part of the ring 40. Three
modules 11 provide corresponding pairs of scatter and catcher
detectors 12, 13. Other dimensions than shown may be used. Any
number of modules 11 may be used to form the ring 40. The ring 40
completely surrounds the patient space. Within a housing of a
medical imaging system, the ring 40 connects with a gantry 50 or
another framework as shown in FIG. 5. The ring 40 may be positioned
to allow a patient bed 60 to move a patient into and/or through the
ring 40. FIG. 6 shows an example of this configuration.
The ring may be used for Compton-based imaging of emissions from a
patient. FIG. 7 shows an example of using the same type of modules
11 but in a different configuration. A partial ring 40 is formed.
One or more gaps 70 are provided in the ring 40. This may allow for
other components to be used in the gaps and/or to make a less
costly system by using fewer modules 11.
FIG. 8 shows another configuration of modules 11. The ring 40 is a
full ring. Additional partial rings 80 are stacked axially relative
to the bed 60 or patient space, extending the axial extent of
detected emissions. The partial rings 80 are in an every other or
every group of N modules 11 (e.g., N=4) distribution rather than
the two gaps 70 partial ring 40 of FIG. 7. The additional rings may
be full rings. The full ring 40 may be a partial ring 80. The
different rings 40 and/or partial rings 80 are stacked axially with
no or little (e.g., less than 1/2 a module's 11 axial extent)
apart. Wider spacing may be provided, such as having a gap of more
than one module's 11 axial extent.
FIG. 9 shows yet another configuration of modules 11. One module 11
or a single group of modules 11 is positioned by the patient space
or bed 60. Multiple spaced apart single modules 11 or groups (e.g.,
group of four) may be provided at different locations relative to
the bed 60 and/or patient space.
In any of the configurations, the modules 11 are held in position
by attachment to a gantry, gantries, and/or other framework. The
hold is releasable, such as using bolts or screws. The desired
number of modules 11 are used to assemble the desired configuration
for a given medical imaging system. The gathered modules 11 are
mounted in the medical imaging system, defining or relative to the
patient space. The result is a Compton sensor for imaging the
patient.
The bed 60 may move the patient to scan different parts of the
patient at different times. Alternatively or additionally, the
gantry 50 moves the modules 11 forming the Compton sensor. The
gantry 50 translates axially along the patient space and/or rotates
the Compton sensor around the patient space (i.e., rotating about
the long axis of the bed 60 and/or patient). Other rotations and/or
translations may be provided, such as rotating the modules 11 about
an axis non-parallel to the long axis of the bed 60 or patient.
Combinations of different translations and/or rotations may be
provided.
The medical imaging system with the Compton sensor is used as a
stand alone imaging system. Compton sensing is used to measure
distribution of radiopharmaceutical in the patient. For example,
the full ring 40, partial ring 40, and/or axially stacked rings 40,
80 are used as a Compton-based imaging system.
In other embodiments, the medical imaging system is a
multi-modality imaging system. The Compton sensor formed by the
modules 11 is one modality, and another modality is also provided.
For example, the other modality is a single photon emission
computed tomography (SPECT), a PET, a CT, or a MR imaging system.
The full ring 40, partial ring 40, axially stacked rings 40,80,
and/or singular module 11 or group of modules 11 are combined with
the sensors for the other type of medical imaging. The Compton
sensor may share a bed 60 with the other modality, such as being
positioned along a long axis of the bed 60 where the bed positions
the patient in the Compton sensor in one direction and in the other
modality in the other direction.
The Compton sensor may share an outer housing with the other
modality. For example, the full ring 40, partial ring 40, axially
stacked rings 40,80, and/or singular module 11 or group of modules
11 are arranged within a same imaging system housing for the sensor
or sensors of the other modality. The bed 60 positions the patient
within the imaging system housing relative to the desired sensor.
The Compton sensor may be positioned adjacent to the other sensors
axially and/or in a gap at a same axial location. In one
embodiment, the partial ring 40 is used in a computed tomography
system. The gantry holding the x-ray source and the x-ray detector
also holds the modules 11 of the partial ring 40. The x-ray source
is in one gap 70, and the detector is in another gap 70. In another
embodiment, the single module 11 or a sparse distribution of
modules 11 connects with a gantry of a SPECT system. The module 11
is placed adjacent to the gamma camera, so the gantry of the gamma
camera moves the module 11. Alternatively, a collimator may be
positioned between the modules 11 and the patient or between the
scatter and catcher detectors 12, 13, allowing the scatter and/or
catcher detectors 12, 13 of the modules 11 to be used for
photoelectric event detection for SPECT imaging instead of or in
addition to detection of Compton events.
The module-based segmentation of the Compton sensor allows the same
design of modules 11 to be used in any different configurations.
Thus, a different number of modules 11, module position, and/or
configuration of modules 11 may be used for different medical
imaging systems. For example, one arrangement is provided for use
with one type of CT system and a different arrangement (e.g.,
number and/or position of modules 11) is used for a different type
of CT system.
The module-based segmentation of the Compton sensor allows for more
efficient and costly servicing. Rather than replacing an entire
Compton sensor, any module 11 may be disconnected and fixed or
replaced. The modules 11 are individually connectable and
disconnectable from each other and/or the gantry 50. Any bridges
are removed, and then the module 11 is removed from the medical
imaging system while the other modules 11 remain. It is cheaper to
replace an individual module 11. The amount of time to service may
be reduced. Individual components of a defective module 11 may be
easily replaced, such as replacing a scatter or catcher detector
12, 13 while leaving the other. The modules 11 may be configured
for operation with different radioisotopes (i.e., different
energies) by using corresponding detectors 12, 13.
FIGS. 11-15 show embodiments where the modules 11 selectably
include a physical aperture for SPECT detection using the
photoelectric effect. The modules may selectably include a scatter
detector for Compton detection. The modules may be used for both
Compton detection and photoelectric detection. A multi-modality
medical imaging system is formed from one or more of the modules.
The arrangements and components of the modules 11 discussed for
FIGS. 1-9 may be used for the modules 11 with the physical
aperture.
The segmented detection modules 11 may be used to form a geodesic
dome-like multi-layer multi-modal camera. The camera is segmented
into modules that house the detection units. Each module 11 is
independent, and when assembled into a ring, partial ring or other
configuration, the modules 11 may communicate with each other. Each
module 11 includes an inner shell-like layer, denominated scatter
layer, and an outer shell-like layer, denominated catcher layer.
Where multiple modulus 11 are used, the modules may at least partly
surround the imaging object.
FIG. 16 shows an embodiment of a medical imaging system where the
modules 11 do not include the scatter detector, so provides for
modular creation of a SPECT camera using the physical aperture and
a detector. FIG. 15 shows an embodiment of a medical imaging system
where the modules 11 include the scatter detector, so provides for
modular creation of a Compton camera using the scatter detector.
The modules 11 of FIG. 15 may include the physical aperture, so
operate both as a Compton camera and a SPECT camera. Depending on
the desired energies to be imaged for any given system, the base
module with the catcher detector may be fitted with either or both
of the scatter detector (e.g., higher energies) or the physical
apertures (e.g., lower energies).
FIG. 11 illustrates the detector structure of one module 11 where
both the physical aperture 110 and the scatter detector 12 are
selected and included in the same module 11. The module 11 includes
the scatter detector 12 and the catcher detector 13. The scatter
detector 12 and/or catcher detector 13 are solid-state detectors,
so the module 11 is a solid-state detector module. A bracket,
frame, clips, or other mechanical structure is provided for
positioning the scatter detector 12 within the module 11 where the
scatter detector 12 is selected to be included. The position may be
at a given distance from the catcher detector 13 or may be
adjustable in assembly or after assembled. Mechanical structures
may be provided for positions of additional catcher and/or scatter
detectors in the module 11 so that the designer of a given imaging
system may select the number of catcher and/or scatter layers to
include.
Additional catcher or scatter detectors 12, 13 may be provided,
such as layering detectors 12, 13 in parallel normal to a radial
from the patient space (e.g., along the axis of rotation in FIG.
11). Any emissions passing through one catcher detector 13 may
interact in another catcher detector 13. Similarly, the
intermediate detectors may operate as scatter detectors 12 due to
an emission passing through the initial scatter detector 12. The
intermediate detectors may have a same structure as either the
scatter detector 12 or the catcher detector 13, but operate as
scatter and/or catcher detectors 12, 13. One of the scatter
detectors 12 generates Compton-scattering photons, which are
captured by one of the sub-sequent catcher layers 13.
The modules 11 are independent yet may be assembled into a unit
that produces multi-modal-based image formation images. The modules
11 allow for the design freedom in the shape to change radius for
each radial detection unit, angular span of one module 11, and/or
axial span. The dimensions and position of the modules 11 relative
to a patient space may be altered in design as needed, such as by
using a different housing.
Any of the shapes described for FIGS. 1-9 may be used. For example,
FIG. 1 shows modules 11 with four sides in cross section orthogonal
to a radial from the patient space. In one embodiment, the modules
11 have three, five, six, or more sides in cross section orthogonal
to a radial from the patient space. FIG. 11 shows a six sided
module 11. Where multiple modules 11 are to be used together, all
the modules have a same number of sides. Alternatively, different
modules 11 with a different number of sides are used together, such
as a combination of modules 11 with five and six sides.
The three, five, or six sided modules have a narrower orthogonal
cross section closer to the patient space than the orthogonal cross
section further from the patient space, allowing for a geodesic
dome. The modules 11 may be positioned to form a sphere or geodesic
dome. For any given imaging system, a full dome is not used. Two or
more modules 11 may be positioned to form part of a geodesic dome.
In alternative embodiments, the modules 11 are not shaped for
forming a sphere or geodesic dome, such as the modules 11 of FIG. 1
being shaped to form a ring or cylinder.
The modules 11 are cylindrically symmetric. A narrowest end of each
of the modules 11 is closest to a patient space of the medical
imaging system. A widest end of each of the modules 11 is further
or furthest from the patient space. The scatter detector 12 is
narrower and has less area than the catcher detector 13.
Where the modules 11 include both a scatter and catcher detectors
12, 13, Compton-based imaging may be provided. To detect events
using the photoelectric effect for SPECT, a physical aperture 110
is included in the module 11. The physical aperture 110 is a plate
or sheet of material. The physical aperture 110 is of any material
that is opaque to lower energy (e.g., at about or less than 140.5
keV), such as lead or tungsten. Any thickness may be used, such as
0.5-5 mm (e.g., 1-3 mm). The thickness is chosen to allow all or
some higher energy emissions or photons (e.g., >>140.5 keV)
to pass for Compton detection.
The physical aperture 110 is positioned between the position for
the scatter detector 12 and the catcher detector 13. Where
intermediate detectors are provided, the physical aperture 110 may
be between any of the detector layers. The coded aperture may be
adjacent to the catcher detector 13, such as within 1 cm (e.g.,
within 5 mm), or spaced further from the catcher detector 13. In
alternative embodiments, the physical aperture 110 is positioned in
front of (i.e., closer to the patient space) of the position for
the scatter detector 12.
A bracket, frame, clips, or other mechanical structure is provided
for positioning the physical aperture 110 within the module 11
where the physical aperture 110 is selected to be included. The
position may be at a given distance from the catcher detector 13 or
may be adjustable in assembly or after assembled.
The physical aperture 110 is orthogonal to the radial from the
patient space, so is parallel with the detectors 12, 13.
Alternatively, the physical aperture 110 is not parallel with one
or both detectors 12, 13 and/or is not orthogonal to the radial
from the patient space. The radial is shown in FIG. 11 as an axis
of rotation.
The physical aperture 110 has a same shape as the detectors 12, 13.
For example and as shown in FIG. 11, the physical aperture 110 and
detectors 12, 13 are six sided. The physical aperture 110 may have
a different outer circumference shape than one or both detectors
12, 13.
The physical aperture 110 is a coded aperture. Holes in a regular
or varying pattern are provided to cast a shadow on the catcher
detector 13. The holes are of the same or different shapes and/or
sizes. The holes are of sufficient size that emissions from
different angles (e.g., 0-40 degrees away from orthogonal to the
physical aperture 11) may pass through a hole. The coding in the
holes of the aperture cause overlapping shadows on the catcher
detector 13 as illuminated from a source (e.g., patient). The
coding of the shadows may be used as a mask in reconstruction to
deconvolve an image. In alternative embodiments, the physical
aperture 110 is a parallel hole collimator (e.g., only emissions
0-1 degree from orthogonal pass through a hole).
To reduce noise, source size, and/or scattering problems, the coded
aperture may be a time-encoded aperture. The physical aperture 110
rotates about a center axis (e.g., radial from the patient space).
The coding in the shadow is shifted or changed for detecting at
different times. Detections from different positions of the coded
aperture 110 relative to the catcher detector 13 are used to reduce
noise and/or distinguish background emissions from emissions from
the patient. The time-encoded coded-aperture near the catcher
detector 13 rotates around the axis of rotation to improve image
quality and increase the field of view. In other embodiments, the
physical aperture 110 translates instead or in addition to
rotating. The translation shifts the position of the physical
aperture 110 relative to the catcher detector 13 within the module
11. Other time encoding may be used.
In one embodiment, the physical aperture 110 is positioned relative
to the catcher detector to cast the shadow on a center region 112
of the catcher detector 13 and not an outer region 114 of the
catcher detector 13. For example, the physical aperture 110 has a
same or similar (e.g., within 10%) area as the scatter detector 12
and a lesser area than the catcher detector 13. Due to scattering
in Compton detection, the photons detected by the catcher layer for
the Compton effect are more likely to be away from the center of
the catcher detector 13. Conversely, since scattering is not used
for the photoelectric effect, the photons detected using the
photoelectric effect are more likely to be in the center region
112. The center region 112 records Compton scattered photons as
well as photoelectric events that do not interact with inner
detectors. The outer region 114 records only or mostly Compton
scattered events from inner scatter detector 12 or other scatter
detectors 12.
The actual structure of the catcher detector 13 may be uniform or
the same for both the central region 112 and the outer region 114,
but may have different pixel size, thickness, and/or other
characteristics for the different regions 112, 114. The readings
from the catcher detector 13 may be limited to one or both regions
112, 114 based on the type of imaging performed. Alternatively,
different structure is used, or detection over the entire catcher
detector 13 is used regardless of the type of imaging. Where
modules 11 are arranged to communicate, Compton events from one
module 11 may be detected with either region 112, 114 of another
module 11.
The image processor 19 is configured to detect emissions with a
photoelectric effect using the physical aperture 110 and the
catcher detector 13 and to detect emissions with a Compton effect
using the scatter detector 12 and the catcher detector 13. The
detected events output by the circuit boards 14 are used by the
image processor 19 for SPECT or Compton imaging. For SPECT, the
coded or time-encoded aperture is used without events from the
scatter detector 12. Photons at energies at about 140.5 keV or less
are detected using the photoelectric effect. For Compton scatter,
the scatter detector 12 and catcher detector 13 are used without
the shadowing from the physical aperture 110. Photons at energies
an order of magnitude larger (e.g., 1450 keV or larger) are
detected using the Compton effect. The same modules 11 and image
processor 19 are used for both photoelectric and Compton
imaging.
For Compton detection, the events from the scatter and catcher
detectors 12, 13 are paired and used to determine angles of
incidence for Compton events in one or more modules 11. Photons may
interact first in the scatter-layer(s) by Compton-scatter and then
in the catcher-layer by photoelectric effect. These photons trigger
both the scatter-layer(s) and the catcher-layer and deposit their
full energy on all layers (multi-layer event). Due to scattering,
over half or most of the events detected in the catcher detector 13
are in the outer region 114. The photon interaction events are
primarily (over half or most) detected in the outer region 114.
Compton reconstruction is used to determine the correct source
direction by knowing (estimating) the Compton kinematics based on
measured position (x,y,z) and energy (E) for paired events.
For photoelectric detection (i.e., SPECT imaging), photoelectric
events from the catcher detector 13 are counted. The physical
apertures 110 and catcher detectors 13 of the modules 11 are used.
Photons may interact only in the catcher-layer by the photoelectric
effect. The low energy photons may not trigger the scatter-layer
and instead deposit their full energy on the catcher-layer
(single-layer event). Since scattering is not used, the
photoelectric events are counted from the center region 112 and not
the outer region 114 of the catcher detector 13. Events from the
outer region 114 may be used as measures of background.
A time-encoded coded-aperture may rotate around the axis of the
module 11 and is used to determine the correct source direction.
The time-encoded coded-aperture may reduce background (e.g.,
scatter, higher energy photons emitted by the source, etc.).
The image processor 19 is configured to generate a SPECT image. The
counts and the positions on the catcher detector 13 (i.e.,
positions indicating the lines of response) are used to reconstruct
a two or three-dimensional representation of the patient. The
locations of emissions are represented. The image processor 19 is
configured to generate a Compton image from the Compton events. A
two or three-dimensional representation is reconstructed from the
Compton scatter events and the corresponding estimated angles. For
a three-dimensional representation of the object or image space, a
two-dimensional image may be three-dimensionally rendered from the
representation.
The display 22 is a CRT, LCD, projector, printer, or other display.
The display 22 is configured to display the SPECT image and/or the
Compton image. The image or images are stored in a display plane
buffer and read out to the display 22. The images may be displayed
separately or are combined, such as displaying the Compton image
overlaid with or adjacent to the SPECT image.
FIGS. 12-16 show medical imaging systems formed from two or more
modules 11. The shape of the solid-state detector modules 11 allow
the modules 11 to stack together with or without direct contact to
form part of a geodesic dome. The modules 11 may be combined to
form a 3D geodesic dome-like SPECT-Compton camera. FIGS. 12-16 show
different realizations of the same concept having 18, 34, 54, 3 and
3, modules respectively.
FIG. 12 shows the modules 11 used to form a full ring 120. Based on
the radius of the ring and size of the modules 11, eighteen modules
11 form the full ring 120. More or fewer modules 11 may be used to
form the full ring 120. One or more partial rings may be formed
instead.
FIG. 13 shows the modules 11 used to form two full rings 130, 132.
The two rings 130, 132 intersect, so share two of the modules 134.
One of the rings 130 is at 90 degrees to the other ring 132.
Depending on the number of sides and/or the shape of the modules
134, other angles may be provided. In the example of FIG. 13,
thirty-four modules 11 form the two rings 130, 132. Other numbers
of modules 11 may be used. One or both rings 130, 132 may be
partial rings. The rings 130, 132 are separate but intersect. In
other embodiments, the rings 130, 132 do not intersect and are
spaced from each other in parallel or non-parallel planes.
Additional rings may be included.
The rings 130, 132 are held in place or stationary. In other
embodiments, the rings 130, 132 connect to hinges or a rotary axis.
The rings 130, 132 pivot about a common axis, such as an axis
through the two shared modules 134. Translation and/or rotation of
both rings 130, 132 or each ring 130, 132 independently may be
provided.
FIG. 14 shows the modules 11 used to form three rings into a larger
part of a geodesic dome 140 as compared to FIGS. 12 and 13. Part of
a spherical shell is formed from the segmented modules 11. The
three rings are axially adjacent to each other with little (e.g.,
less than 1/2 width of a module 11) or no separation. The rings may
be in direct contact with each other and/or mounted to a same
gantry or framework. Three full rings are shown, but one or more
rings may be partial rings. Two, four, or more rings may be used.
In the example of FIG. 14, fifty-four modules 11 are used for the
three rings, but additional or fewer number of modules 11 may be
used.
FIG. 15 shows three modules 11 positioned relative to the patient
bed 60. One, two, four, or more modules 11 may be used. The modules
11 are spaced from each other by one or more module widths, but
lesser separation or adjacent placement may be used. The modules 11
may be connected with another modality, such as a dedicated SPECT
camera. The modules 11 connect with a gantry to allow rotation
around and/or translation (e.g., transaxially) along a patient.
Alternatively or additionally, the bed 60 moves the patient
relative to the modules 11.
FIG. 16 shows the three-module arrangement of FIG. 15 using a
different type of module 160. The scatter detector 12 is removed,
allowing the modules 160 to be less high or have a smaller extent
along the radial from the patient space. The same height may be
used, such as using the same housings but without the scatter
detector 12. Compton imaging is not provided, so the modules 160
use the physical aperture 110 with one or more catcher detectors
13. The catcher detector 13 functions with the time encoded coded
aperture 110 for SPECT or photoelectric effect-based imaging. The
catcher detector 13 absorbs photons by the photoelectric effect.
The time encoded coded-aperture 110 near the catcher layer may
rotate around the axis of rotation to improve image quality. The
coded aperture may also move in the XY detector plane (sideways) to
increase the field of view. Other arrangements of the modules 160
for SPECT imaging may be used, such as the arrangements of FIGS.
12-14. A single module 160 may be used. Less or more modules built
in any of different configurations may be used.
FIG. 10 shows one embodiment of a flow chart of a method for
forming, using, and repairing a camera selectable to be a Compton
camera, a SPECT camera, or both. The camera is formed in a
segmented approach. Rather than hand assembling the entire camera
in place, one or more catcher detectors are positioned relative to
each other to form a desired configuration of the camera. The
catcher detectors are arranged to be usable for relatively lower
emission energies with a coded aperture and to be usable for
relatively higher emission energies with a scatter detector. This
selectable and segmented approach may allow different
configurations using the same parts, ease of assembly, ease of
repair, and/or integration with other imaging modalities.
Other embodiments form a combination of a Compton camera and a
SPECT camera where both the scatter detector and coded apertures
are selected to be used in a same camera with the catcher detector.
The segmented module 11 of FIG. 11 is used. The modules 160 of FIG.
16 may be used for forming a SPECT camera without the scatter
detector being included. The modules 11 of FIG. 11 may be used for
forming a Compton camera without the coded apertures.
The method may be implemented by the system of FIG. 1 to assemble a
Compton sensor as shown in any of FIGS. 4-9. The method may be
implemented by the system of FIG. 11 to assemble a Compton sensor
as shown in any of FIGS. 12-16. Other systems, modules, and/or
configured Compton sensors may be used.
The acts are performed in the order shown (i.e., top to bottom or
numerically) or other orders. For example, act 108 may be performed
as part of act 104.
Additional, different, or fewer acts may be provided. For example,
acts 102 and 104 are provided for assembling the Compton camera
without performing acts 106 and 108. As another example, act 106 is
performed without other acts.
In act 102, catcher detectors are housed in separate housings.
Modules are assembled where each module includes a catcher
detector. A machine and/or person manufactures the housings. Only
one housing and corresponding module may be used.
The modules are shaped to abut where the scatter and catcher
detector pairs of different ones of the housings are non-planar.
For example, a wedge shape and/or positioning is provided so that
the detector pairs from an arc, such as shown in FIG. 4C. The shape
allows and/or forces the arc shape when the modules are positioned
against one another.
For the Compton-SPECT camera (e.g., FIG. 11), the scatter detector,
coded aperture, and catcher detector are housed in a housing. The
housings and corresponding modules have any shape, such as being
shaped to be part of or form part of a geodesic dome. The housing
selectably includes one or both of the scatter detector and the
coded aperture. Depending on the design and/or emission energy
requirements, the same housing with positions for both the scatter
detector and the coded aperture may be used even where only one of
the scatter detector or coded aperture are positioned or installed.
Alternatively, different housings are used depending on which of
the scatter detector and/or coded aperture are to be included.
In act 104, the housings are abutted. A person or machine assembles
the Compton sensor from the housings. By stacking the housings
adjacent to each other with direct contact or contact through
spacers, gantry, or framework, the abutted housings form the arc. A
full ring or partial ring is formed around and at least in part
defines a patient space. Based on the design of the Compton camera,
SPECT camera, or Compton-SPECT camera, any number of housings with
the corresponding scatter and catcher detector pairs are positioned
together to form a camera. A single housing may be used.
The housings may be abutted as part of a multi-modality system or
to create a single imaging system. For a multi-modality system, the
housings are positioned in a same outer housing and/or relative to
a same bed as the sensors for the other modality, such as SPECT,
PET, CT, or MR imaging system. The same or different gantry or
support framework may be used for the housings of the Compton
camera and the sensors for the other modality. For the embodiments
of FIGS. 11-15, the modules provide the multi-modality by providing
for both a Compton camera and the SPECT imaging system.
The configuration or design of the Compton camera defines the
number and/or position of the housings. Once abutted, the housings
may be connected for communications, such as through one or more
bridges. The housings may be connected with other components, such
as an air cooling system and/or a Compton processor.
In act 106, the assembled Compton camera detects emissions. A given
emitted photon interacts with the scatter detector. The result is
scattering of another photon at a particular angle from the line of
incidence of the emitted photon. This secondary photon has a lesser
energy. The secondary photon is detected by the catcher detector.
Based on the energy and timing of both the detected scatter event
and catcher event, the events are paired. The positions and
energies for the paired events provides a line between the
detectors and an angle of scattering. As a result, the line of
incidence of the emitted photon is determined.
To increase the likelihood of detecting the secondary photon, the
catcher events from one housing may be paired with the scatter
events of another housing. Due to the angles, scatter from one
scatter detector may be incident on the paired catcher detector in
the same housing or a catcher detector in another housing. By the
housings being open in the detector region and/or using low photon
attenuating materials, a greater number of Compton events may be
detected.
The detected events are counted or collected. The lines of response
or lines along which the different Compton events occur are used in
reconstruction. The distribution in three dimensions of the
emissions from the patient may be reconstructed based on the
Compton sensing. The reconstruction does not need a collimator as
the Compton sensing accounts for or provides the angle in incidence
of the emitted photon.
Using the Compton-SPECT modules 11 of FIG. 11, the modules may also
be used to detect emissions as photoelectric events. The lower
energy emissions pass through the scatter detector. These emissions
may pass through holes in the coded aperture or are blocked by the
coded aperture. The catcher detector detects at least some of the
emissions passing through the holes of the coded aperture.
Depending on the selection to include either or both of the scatter
detector and coded aperture, emissions at relatively lower and/or
higher energies are detected.
The detected events are used to reconstruct the locations of the
radioisotope. Compton and/or photoelectric images are generated
from the detected events and corresponding line information from
the events.
In act 108, a person or machine (e.g., robot) removes one of the
housings. When one of the detectors or associated electronics of a
housing fails or is to be replaced for detecting at different
energies, the housing may be removed. The other housings are left
in the medical imaging system. This allows for easier repair and/or
replacement of the housing and/or detectors without the cost of a
greater disassembly and/or replacement of the entire Compton
camera.
While the invention has been described above by reference to
various embodiments, it should be understood that many changes and
modifications can be made without departing from the scope of the
invention. It is therefore intended that the foregoing detailed
description be regarded as illustrative rather than limiting, and
that it be understood that it is the following claims, including
all equivalents, that are intended to define the spirit and scope
of this invention.
* * * * *